Ion implantation is a type of process that may be performed on, among others, a semiconductor to alter its mechanical, optical, and electrical properties. Among other tools, a beam-line ion implanter may be used. A block diagram of a conventional ion implanter is shown in FIG. 1. The conventional ion implanter may comprise an ion source 102 that may be biased by a power supply 104 and that generates ions. The ion source 102 is typically contained in a vacuum chamber known as a source housing (not shown). In the ion source 102, a filament (not shown) for emitting electrons may be disposed.
The ion implanter system 100 may also comprise a series of beam-line components, through which the ions 10 may pass. The series of beam-line components may include, for example, extraction electrodes 106, a 90° magnet analyzer 108, a first deceleration (D1) stage 110, a 70° magnet collimator 112, and a second deceleration (D2) stage 114. Typically, the wafer 116 may be mounted on a platen 118 that can be moved in one or more dimensions (e.g., translate, rotate, and tilt) by an apparatus, sometimes referred to as a “roplat” (not shown).
In operation, feed gas may be introduced into the ion source 102. Depending on the type of desired ions species, different types of feed gas may be used. For generating dopants for p-type doping, boron trifluoride (“BF3”) feed gas may be introduced to the ion source. For generating Hydrogen (“H”) and Helium (“He”) ions for cleaving process, H2 and He feed gas may be introduced. For generating molecular p-type ions for low energy p-type doping, carborane (CxByHz) and decaborane (“B10H14”) may be introduced. For generating dopants for n-type doping, phospine (“PH3”) or arsine (“AsH3”) feed gas may be introduced to the ion source.
After the feed gas is introduced, the filament may be powered to emit electrons. The electrons may then excite the feed gas into plasma containing charged and neutral particles, the particles including desired ions 10, unwanted ions, and neutrals. The desired ions 10 are extracted through an extraction aperture (not shown) of the ion source 102, manipulated into a beam-like state, and directed toward the wafer 116 by the beam-line components. Unwanted ions may also be extracted, and may be separated from the desired ions 10 through the use of a mass analyzer magnet.
Depending on the species contained in the feed gas, ions and neutrals in the ion source 102 may condense and coat the internal wall of the ion source 102, the extraction aperture, and/or the extraction electrode 106. If, for example, carborane or diborane feed gas is used, the internal wall of the ion source 102 may be coated with, among others, a film containing carbon or boron. The coating may change the electrical characteristics of the ion source 102 or even cause ion source 102 failure. In addition, the deposited layer may act as a source for contamination in subsequent implantation.
To prevent excess coating, the ion source 102 is cleaned periodically. After performing several ion implantations, the ion source 102 may be removed from the implantation system 100, taken apart, and cleaned. However, such a process does not adequately and efficiently clean the ion source 102. In addition, the cost of the cleaning process may be high, placing additional financial burden on semiconductor device manufacturers and, ultimately, consumers. As such, a new ion source and ion source cleaning method are needed.